**Core Concept**
Papillary carcinoma is the most common type of thyroid cancer, accounting for approximately 70-80% of all thyroid cancer cases. It is a well-differentiated cancer that arises from the follicular cells of the thyroid gland.

**Why the Correct Answer is Right**
Papillary carcinoma is characterized by its distinctive nuclear features, including nuclear grooves, pseudoinclusions, and ground-glass appearance. These features are a result of the abnormal growth and differentiation of thyroid follicular cells. The cancer cells often spread to regional lymph nodes, but it is generally a slow-growing cancer with a good prognosis if diagnosed early. The high incidence of papillary carcinoma can be attributed to its association with radiation exposure, particularly in childhood.

**Why Each Wrong Option is Incorrect**
**Option A:** Anaplastic carcinoma is a rare and aggressive form of thyroid cancer, accounting for only 1-2% of all thyroid cancer cases. It is characterized by its rapid growth and poor prognosis.
**Option B:** Follicular carcinoma is the second most common type of thyroid cancer, but it accounts for only 10-15% of all thyroid cancer cases. It is a well-differentiated cancer that arises from the follicular cells of the thyroid gland, but it is more aggressive than papillary carcinoma.
**Option D:** Medullary carcinoma is a rare type of thyroid cancer that arises from the parafollicular cells of the thyroid gland. It accounts for only 3-5% of all thyroid cancer cases and is often associated with genetic mutations.

**Clinical Pearl / High-Yield Fact**
Papillary carcinoma is often associated with radiation exposure, particularly in childhood. Therefore, patients with a history of radiation exposure should be screened for thyroid cancer, especially if they have a family history of the disease.

**✓ Correct Answer: C. Papillary carcinoma**